Some previously known paint conveying systems include a diaphragm pump in a closed housing. The diaphragm pump may also include an admission valve and a discharge valve, and be driveable with an asynchronous electric motor that can be switched by a manometric switch dependent on the conveying pressure. The motors in such systems typically use a capacitor, and are arranged in a housing formed of two housing shells joined together. Typically, the housing is laterally provided with two connecting sleeves, arranged parallel to one another, to connect the conveying apparatus to the reservoir and the application device, respectively.
The size and weight of the asynchronous motors used in previously known paint conveying apparatus render such devices large and unwieldy. Since the heft of such conveying apparatus precludes the use of a portable reservoir, painting large areas requires long paint conducting lines to reach a stationary reservoir. Further, it is impossible to optimize the torque output of the asynchronous motor to the input power required by the diaphragm pump, since the motor acts directly on the diaphragm of the pump via a connecting rod. Another major disadvantage is that additional tools are required for cleaning the admission valve and/or the discharge valve in order to be able to screw the valves out of the housing. It is imperative for proper operation of the device that these valves be frequently cleaned, which requires significant time expenditure and results in long operating interruptions. The adjustment of the manometric switch is also complicated, since adjustment requires that both a ram and an adjustment screw, as well as a coil pressure spring, must be set.